Sometimes referred to as microbial Eve our last common ancestor was a single celled organism that lived when the Earth was in its Hadean era 4 billion years ago. Our LUCA was likely an extremophile organism that lived in an area where sea water and magma met.
We first saw plants and animals on Earth 500 million years ago during the Cambrian period. The first animals were Comb Jellies that dwelled in the ocean. The first land mammals were small rodents similar to mice. The first plants on land were mosses and liverworts.
The first primate mammals evolved during the Paleocene Epoch during the Cenozoic era (65-55 million years ago). They were similar to squirrels and fossil evidence shows they preferred warm and damp climates. Historians and scientists estimate they had fair eyesight and good climbing ability.